Why are the Fundy Tides the Highest in the World?

While the gravitational forces of the sun and moon combine to create a continuum of tidal action the world over, it is the unique shape of the Bay of Fundy that contributes to the extraordinary high tides experienced here.

The Bay of Fundy is 290-kilometer-long (180 miles) in length. The mouth of the Bay is 100 km (62 miles) wide and between 120 and 215 meters (400-700 feet) deep. Frequently described as funnel-shaped, this amazing body of water gradually narrows until it splits to form Chignecto Bay and the Minas Basin. Becoming gradually shallower, Chignecto Bay splits into Shepody Bay and Cumberland Basin, then Shepody Bay narrows and splits again into the Memramcook and Petitcodiac Rivers.

It is here, near this junction of rivers that the Hopewell Rocks are found. The distance across the Bay at this point is about 2.5 km (1.5 miles) and the depth at low tide about 14 meters (45 feet).

The great tides of the Bay of Fundy are due to two unique characteristics of this finger of the Gulf. The gradual tapering and shallowing that constricts the tidal flow into Bay, causes the waters to rise from an average of one meter (3 feet) found elsewhere to the 16-meter (52 feet) tidal range found at the head of the bay.

The second factor is the precise dimension of this incredible body of water. Every basin of water has its own natural rhythm and at 290 km (180 miles) long, the time it takes for the tide to flood the length of Bay of Fundy is nearly identical to the time it takes for the tide to come in from the adjoining Gulf of Maine.

This resonance - the meshing of these two rhythms - means that the tidal range is amplified. Called the "Seiche Effect", this amplification is frequently compared to the wave action produced by a child sloshing water back and forth in a bathtub, each wave higher than the one previous. It is this comparison which led to the Bay of Fundy being called 'the world's largest bathtub'.